The present invention relates to a liquid-crystal display device and a method of manufacturing the same and, more particularly, to an inner surface structure of a substrate constituting a liquid-crystal panel.
A liquid-crystal display device generally comprises a liquid-crystal panel in which two substrates having inner surfaces on which electrodes corresponding to a large number of pixel regions arranged on a display surface are arranged are formed to hold a liquid-crystal layer between the substrates. In order to drive the liquid-crystal display device, an electric field is applied to the liquid-crystal layer by the electrodes to change the optical characteristics of the liquid-crystal layer, so that various displays can be performed. In this case, wiring layers for applying a predetermined drive potential to the electrodes may be arranged in parallel.
In an active matrix liquid-crystal display device, active elements such as TFT (Thin Film Transistors) elements or MIM (Metal-Insulator-Metal) elements are connected to the wiring layers formed on the inner surfaces of element substrates. These active elements are connected to pixel electrodes formed in pixel regions, respectively.
Some liquid-crystal display devices capable of performing a color display have the following structure. That is, color resists or the like each having a predetermined pattern are formed on the inner surface of the opposite substrate opposing an element substrate on which the active elements are formed, so that a color filter in which coloring layers, i.e., red (R), green (G), and blue (B) layers are formed. The color filter is covered with an overcoat film, and an opposite transparent electrode consisting of an ITO (Indium-Tin Oxide) is formed.
In the above conventional liquid-crystal display device, a liquid-crystal layer is sealed between two substrates, and a predetermined voltage is applied across two opposite electrodes formed on the inner surfaces of both the substrates to change the orientation of liquid-crystal molecules. However, in steps in manufacturing the liquid-crystal display device, conductive foreign matter may be inserted between the two substrates or into the liquid crystal. In this case, the conductive foreign matter may be interposed between the electrodes formed on the two substrates to adversely affect an electric field to be applied to the liquid crystal, or a point defect may be generated by the short circuit between the electrodes.
Here, even if the conductive foreign matter is inserted into a pixel region to short-circuit the electrodes, only the corresponding pixel is not operated in the active matrix liquid-crystal display device, i.e., only a point defect is generated. However, if similar foreign matter is located above a wiring layer or an active element on an element substrate, the wiring layer and the opposite electrode may be short-circuited. In this case, a crossline-like line defect may be generated on the display surface. Unlike the above point defect, generation of such a line defect means that a liquid-crystal panel is defective. Therefore, the line defect considerably degrades the manufacturing yield of the liquid-crystal display device to seriously affect manufacturing steps or manufacturing cost.
In particular, even if abnormality is not detected in the manufacturing steps, such a defect caused by conductive foreign matter may be retroactively generated by the foreign matter moving in the panel after shipping. For this reason, the defect cannot be easily prevented by inspections in the manufacturing steps. Therefore, perfect countermeasures against the defect caused by foreign matter are necessary.
Therefore, the present invention has been made to solve the above problem, and has as its object to prevent a display defect caused by a short circuit between upper and lower electrodes by using a structure in which two substrates in a liquid-crystal display device are not easily short-circuited.
In order to solve the above problem, a means provided by the present invention is a liquid-crystal display device comprising two substrates which interpose a liquid-crystal layer therebetween, a wiring layer formed on at least one inner surface of the substrates, and a pixel electrode directly or indirectly connected to a connection portion of the wiring layer, characterized in that an insulating film is formed on a surface of the wiring layer.
According to this means, when the surface of the wiring layer is covered with the insulating layer, contact of conductive foreign matter to the wiring layer and a short circuit between the wiring layer and the opposite electrode through the foreign matter can be prevented, and a severe line defect can be prevented from being generated.
Here, the insulating film is preferably arranged to insulate the wiring layer and the pixel electrode from each other, and preferably has an opening for assuring the electric conductivity between the connection portion and the pixel electrode.
According to this means, since the insulating film is formed not only to insulate the surface of the wiring layer, but also to insulate the wiring layer and the pixel electrode from each other, the wiring layer and the pixel electrode are not in contact with each other except for the electric conductive portion between the connection portion and the pixel electrode. For this reason, degradation of a display state caused by the short circuit between the wiring layer and the pixel electrode can be prevented.
A MIM element is formed between the connection portion and the pixel electrode, and the insulating film preferably also covers the surface of the MIM element.
According to this means, since the insulating film also covers the surface of the MIM element, contact between the MIM element and conductive foreign matter and a short circuit between the MIM element and the opposite electrode through the foreign matter can be prevented.
A TFT element is formed between the connection portion and the pixel electrode, and the insulating film is preferably formed on the wiring layer connected to the TFT element.
According to this means, contact between the wiring layer connected to the TFT element and conductive foreign matter and a short circuit between the wiring layer and the opposite electrode through the foreign matter can be prevented.
The insulating film preferably has light-shielding properties.
According to this means, since a light-shielding member need not be arranged on a substrate on which a color filter is formed, manufacturing cost can be reduced, and the opposite electrodes need not be arranged with a high alignment precision.
In a method of manufacturing a liquid-crystal display device comprising two substrates which interpose a liquid-crystal layer therebetween, a wiring layer formed on at least one inner surface of the substrates, and a pixel electrode directly or indirectly connected to a connection portion of the wiring layer,
after the wiring layer is formed on the inner surface of the substrates, an insulating film is formed to cover the surface of the wiring layer and a portion between the wiring layer and the pixel electrode, and then, the pixel electrode is formed such that the peripheral portion of the pixel electrode is arranged on the insulating film.
According to this means, the surface of the wiring layer can be covered with the insulating film, and the wiring layer and the pixel electrode can be insulated from each other by the insulating film. For this reason, the insulating properties between the opposite substrates and the insulating properties between the wiring layer and the pixel electrode can be assured.
In this case, after a MIM element connected between the connection portion and the pixel electrode is formed, the insulating film is preferably formed to also cover the surface of the MIM element.